Audio pickup device



Patented June 30, 1953 UNITE-D STATES PATENT OFFICE AUDIO PICKUP DEVICECharles C. McCracken, Chicago, Ill.

Application April 4, 1951, Serial N o. 219,243

1. Claim.

The present invention relates tovaudio pickup devices nding particularthough by no means exclusive utility in connection with hearing aids.

It is a general object of the present invention to provide a novelattachment for a hearing aid which makes the reproduction of sound morepleasant to the user and which increases the ef'- fectiveness of the aidin overcoming deciencies in hearing. v

Another object of the invention is to provide an audio pickupdeviceincluding a microphone element together with physical meansoperative to limit maximum loudness to the end that reproduction ofsharp or sudden noise impulses is minimized.

A further object is to provide an' audio pickup device of the abovegeneral character in a hearing aid whereby to eliminate painful anddisturbing sensations to the user which result from Sharp noises such,for example, as those produced by a slamming door, a clanging'bell, `orthe like.

Still another object lies in the provision of means of a simplecharacter which is effective with the aforementioned audio pickupdeviceto minimize the objectionable noises incident to the wearing of ahearing aid known as clothing scratch.

The objects of the inventionV thus generally set forth together withother objects and ancillary advantages are attained by the constructionand arrangement shownby `way of illustration in the accompanyingdrawing,r in which: Y

Figure l is a perspective View of a hearing aid including an audiopickup device embodying the features of thel present invention.

Fig. 2 is a fragmentary vertical section taken substantially inthefplane of li-ne 2 2 in Fig. 1.

Fig. 3 is a perspective view of a modied form of hearing aid embodyingthe features of the present invention.

Fig. 4 is a vertical section taken substantially in the plane of line4--4 in Fig. 3.

Fig. 5 is a' fragmentary elevational view of a microphone arrangementintended for use with public address `systems and the like and showingin dotted section an audio' pickup device embodying the features of theinvention.

While illustrative embodiments of the invention have been shown in thedrawing and will herein be described in detail. it is to be understoodthat the intention is not to limit the invention to the specificembodiments shown, but, on the contrary, it is intended to cover allmodiiications and alternative constructions falling within the spiritand scope of the inventicn as expressed in the appended claim,

Users of hearing aids have been continuallyy plagued by the reproductionby the aids of sharp disturbing noises and scratches. For this reasonnumerous attempts have been made to overcome or eliminate suchobjectionable noises which attempts include the provision of acousticallabyrinths, microphone baffles, and various sound absorbing or deadeningschemes. To the same end, much effort has been expended in the design ofelectronic circuits for such devices which serve to limit maximumloudness and to lter out certain frequency ranges. Not only have theseattempts not permitted of economical manufacture, but more important,none has proved entirely effectual.

The present invention provides a means of a simple and practicalcharacter which has proved eifectual to minimize the reproduction ofsuch noises so that when utilized with conventional hearing aid circuitsobjectionable noises are reduced substantially below the discomfortthreshold level. K

In accordance with the invention, there is provided n combination with amicrophone element a passageway or `audio canal to the microphoneelement for the conduction of an audio wave thereto, and an audio filtershield arranged at the outer end of the passageway` surrounding thesame, for receiving and guiding an audio wave impinging thereon intosaid passageway. The audio filter shield has a flared portion which liespredominantly ony one side of the passageway, its surface beinginterrupted by generally longitudinal ridges 'and valleys and having acurled peripheral flange, the same being formed in the manner of a humanear.

By way of illustration. an audio pickup device I!) embodying the instantinvention is shown applied to a conventional hearing aid which includesa generally rectangular case l 2, The case i2 may conveniently be formedof a thermosetting plastic. In the form of the invention illustrated inFigs. l and 2, the audio pickup deviceV Iii .is formed integral with thehearing aid case I 2 and includes a passageway or canal Hi formed by atubular projection I6 extending inwardly from the front wall of thehearing aid case v l2. A microphone element, generally designated i8, issupported adjacent the inner end of the passageway I4 in any suitablemanner. Preferably the microphone I8 is enclosed within a resilientcoverm ing 2li which serves both to shock-mount the same and to shieldit from the reception of audio waves from directions other than by wayof the passageway I4.

The outer end of the passageway I4 is out wardly iiared and mergessmoothly with an audio filter shield 22 which, as above noted, is formedintegral with the case I2. The shield 22 is of inverted, generallypear-shaped outline and in 5 cludes a curled peripheral flange or helix2 bordering a depressed valley area 2E. Adia nt to the valley area is anarcuate, generally lo tudinal ridge or antihelix 2S `which bordersflared open end or concha of the passageway irl. 1 The shield alsoincludes an arcuate tab-dike projection or tragus 29 which partiallyoverlies the outer end of the passageway is at one side thereof.

Another form of the invention is shown in Figs. 3 and 4 wherein theaudio pickup device i8 is formed separately from the case 2A of thehearing aid in which it is incorporated. Preferu ably the case I2A isprovided with an inwa ly extending boss 30 which denes a recess 332within which the pickup device I is partially re ceived. Adjacent thelower right-hand corner of the boss is provided an opening .ifi for thereception of the tubular projection le of the pick up device whichdefines the passageway or audio canal I4. The microphone element It ofthe device is, of course, disposed at the inner end of the passageway I4as previously described.

In this instance the audio filter shield 2'? and. the tubular projectionIii comprise a or molding of resilient material such, for as soft rubberor pliable plastic. As shown, the microphone element I8 is molded withinthe projection I6 and the latter is provided with an irrtegral rear wallIa so as to completely enclose the microphone element I8.

Hearing aids are usually supported on an inne'1 garment in a manner suchthat they are li' rom View by an outer garment. For exa la theinstrument may be supported in a shirt pocket and concealed by thewearers coat. This Y jects the instrument to highly objection noiseresulting from therubbing together oi t' a outer layer of clothingagainst the'inner cr rui- Mi lying layer, or by the rubbing of an outerlayer directly against the case of the instrument. The noise produced bythis rubbing together of clothing layers produces substantially the samesensa"- tion to the wearer of the instrument as that prem duced in thenormal ear by the rubbing together of two pieces of sandpaper. In orderto climi-- nate the production of such noise, or at least to minimizethe same, the hearing aid ifi/.A is provided with a covering or envelope[iu of soft, resilient, porous material such, for example, 55 spongerubber. An opening 42 is provided in the covering of the same generalshape as of the recess 32 and the audio pickup device Iii in order notto hinder the operation of the latter and block off the impingement ofaudio air waves thereon.

It will be observed that the inner surface of the covering 4D liesintimately against the outer surface of the hearing aid casing IZA. Thusthere is substantially no relative motion between these two surfaces. Ifdesired, the covering may be fixed to the casing I2A as by cementing. Byvirtue of the soft resilient character of the covering 40 a layer ofclothing bearing thereon tends to cling to the outer surface of thecovering and not slide thereover. It will be apparent, therefore, thatsince there is substantially no movement between the covering 4t and thecase I2A, and little or no movement between the clothing layer and theouter surface of the covering even though the clothing layer might morewith respect to the casing I2A, such moi/ein will be accommodated withinthe resilient coveru ing 40 without the production of any rasping orscratching noise. Should there be movement the clothing layer withrespect to the cove the character of the covering not only minii anynoise production but also will absorb it to the end that it is notpicked up by the audio device IU.

Turning now to Fig. 5 of the drawing, there shown is an acoustic pickupdevice incorporated within a microphone structure for a conventionalpublic address system or the like. As shown, the structure includes anaudio pickup device It like that illustrated in Figs. 3 and 4 housedwithin a generally ellipsoidal casing Sii. The latter includes animperforate rear shell porm tion 50a and a foraminated or mesh frontportion 5017, and the composite structure is sup ported on a suitablestand 52. The audio filter shield 22 is disposed substantially in thetransverse plane defined by the junction between the two casing sections50a and 50D, substantially transversely of the casing 50.

It has been Observed that the use of an audio pickup device of thecharacter described with conventional amplifying equipment operates tosubstantially eliminate the production of reedback unless the device isplaced directly in front of and in close proximity to the speaker ofsuch equipment.

I claim as my invention:

In a hearing aid having a microphone element, the combination of a casefor the hearing aid and an audio pickup device, the latter comprisingmeans defining a canal for conducting an audio wave to the microphoneelement disposed within said case, and an audio filter shield arrangedat the outer end of said canal and generally surrounding the same, saidfilter shield including a flared portion lying predominantly on one sideof said canal and including a tablike projection on the opposite side ofsaid canal partially overlying its outer end, the outer surface of saidiiared shield portion being interrupted by smoothly merging arcuateridges and valleys and terminating in a curled peripheral flange, saidfilter shield being integrally formed with said Acase and lyinggenerally in a plane parallel and closely adjacent the outer surface ofsaid case.

CHARLES C. MCCRACKEN.

' References cited irl the sie of this patent UNITED STATES PATENTSNumber Name Date 1,485,918 Hearn Mar. 4, 1924 1,601,063 Frederick Sept.28, 1925 2,148,477 Koch Aug. 31, 1935 2,468,721 Volkmann Apr. 26, 1949

